Cat flap in external wall

[Questionsquestionsquestions]

This might be a silly question, but if installing a cat flap into a thick external wall, does the actual car repair go on the outside, or the inside? (We're getting some extension tunnel things, but not sure if they go on the inside of it, or the outside?!)
Or do we need to buy two cat flaps?!

Thanks, and sorry if it's a silly question! I've tried googling but can't really find anything!

*the actual cat flap- not car repair!

We have the cat flap on the inside, no need for one on the outside (although I guess it might reduce the very slight draft!)

Our flap is on the inside, tunnel through the wall. It is a microchip flap so the porch of the cat flap that scans the cat is on the outside

We have a lockable flap on the inside and a plain flap on the outside to reduce drafts. The wall faces the prevailing wind. It's worked perfectly for us and the cats.

Thanks all- really helpful!

Another vote for twin flaps.
We have a locking one on the inside (mains powered via a transformer so needed to be adjacent a socket) and a normal one on the outside.
Cats needed to be tempted through with treats for the first time but after that they were fine.
The locking ones operated via a collar worn chip are far better than the old magnet operated ones.

We have two, with the lockable one on the inside. The outside one helps with drafts, stops debris like leaves etc building up in the tunnel, and also looks better when viewed from the garden

@Dougieowner you don’t possibly have a brand name for yours please?

Feels so wasteful to have to keep replacing batteries!

I read the title as Flat Cap in external wall. I thought you'd knocked down an external wall and found a hat in amongst the layers.

I would have the flap on the outside as some cats like to see what's going on outside before going out.

[quote LondonNQT]@Dougieowner you don’t possibly have a brand name for yours please?

Feels so wasteful to have to keep replacing batteries![/quote]
Ours is a Staywell but I can't see a mains powered one listed any more.
Petporte do a similar model.

I know 2 people who spent ££s having cat flaps fitted through external walls and both their cats refused to use them ...

I think my flap is on the outside. The tunnelly bit is on the inside. My cats all use it. (it does get a bit draughty if the flap stays open for some reason).

We had ours on the inside, but our cat was to fat to fit through it and one day she pulled the door off. We now use the hole for the tumble drier tube.